Multitubular heat exchanger

Abstract

A multitubular heat exchanger mainly used in thermal and nuclear power plants having a plurality of tube bundles located within a shell and including a large number of U-shaped heat transfer tubes for permitting a medium to be heated to flow therethrough, and a vent tube interposed between the tube bundles and arranged in the longitudinal direction of the shell, further includes at least one flow guide plate with or without at least one slit disposed in or near the outer marginal portion of one of the tube bundles for inducing streams of a heating medium to flow toward the vent tube. The provision of the guide plate with or without the slit has the effect of moving a heating medium stagnating zone, which has hitherto been located in one of the tube bundles, to a position which is in the vicinity of the vent tube to thereby prevent corrosion of the heat transfer tubes by noncondensable gas.

What is claimed is: 
     
       1. In a feedwater heater comprising a shell, a heating medium inlet formed in said shell, a high temperature tube bundle and a low temperature tube bundle located within said shell and formed by a large number of U-shaped heat transfer tubes for permitting a medium to be heated to flow therethrough so that heat exchange may take place between the medium to be heated and a heating medium introduced into the interior of the shell through the heating medium inlet, and a vent tube interposed between the high temperature tube bundle and the low temperature tube bundle and arranged in the longitudinal direction of the shell for removing noncondensable gas from the interior of the shell, wherein the improvement comprises at least one flow guide plate means located on the outer periphery side of at least the low temperature tube bundle for inducing streams of the heating medium flowing between the shell and the tube bundles to pass on to the vent tube. 
     
     
       2. A feedwater heater as set forth in claim 1, wherein said at least one flow guide plate means is directed toward said vent tube. 
     
     
       3. A feedwater heater as set forth in claim 2, wherein at least one slit cooperating with said at least one flow guide plate means is provided in a manner to open in an outer marginal portion of said low temperature tube handle and extend through the interior of the tube bundle toward the vent tube. 
     
     
       4. A feedwater heater as set forth in claim 3, wherein a portion of said at least one flow guide plate means is disposed within said slit. 
     
     
       5. A feedwater heater comprising a shell, a heating medium inlet formed in said shell, a high temperature tube bundle and a low temperature tube bundle located within said shell and formed by a large number of U-shaped heat transfer tubes for permitting a medium to be heated to flow therethrough so that heat exchange may take place between the medium to be heated and a heating medium introduced into the interior of the shell through the heating medium inlet, and a vent tube interposed between the high temperature tube bundle and the low temperature tube bundle and arranged in the longitudinal direction of the shell for removing noncondensable gas from the interior of the shell, wherein the improvement comprises at least one flow guide plate located on the outer periphery side of at least the low temperature tube bundle for inducing streams of the heating medium flowing between the shell and the tube bundles to pass on to the vent tube. 
     
     
       6. A feedwater heater as set forth in claim 5, wherein at last one slit cooperating with said at least one flow guide plate is provided in a manner to open in an outer marginal portion of said low temperature tube bundle and extending through the interior of the tube bundle toward the vent tube. 
     
     
       7. A feedwater heater as set forth in claim 5, wherein said at least one flow guide plate is directed toward said vent tube. 
     
     
       8. A feedwater heater as set forth in claim 7, wherein there are provided tube support plates for supporting said tube bundles, and said at least one flow guide plate is supported by said tube support plates. 
     
     
       9. A feedwater heater as set forth in claim 7, wherein said at least one flow guide plate is mounted on an inner surface of said shell. 
     
     
       10. A feedwater heater as set forth in claim 7, wherein at least one slit cooperating with said at least one flow guide plate is provided in a manner to open in an outer marginal portion of said low temperature tube bundle and extending through the interior of the tube bundle toward the vent tube. 
     
     
       11. A feedwater heater as set forth in claim 10, wherein a portion of said at least one flow guide plate is disposed within said slit. 
     
     
       12. A feedwater heater as set forth in claim 11, wherein said shell is formed at one end thereof with an inlet water box and an outlet water box for the medium to be heated, and said at least one flow guide plate is mounted for the tube bundle of the heat transfer tubes communicating with said inlet water box for the medium to be heated, which tube bundle is the low temperature tube bundle.